Как в nodeJS запустить несколько потоков чтения/записи одновременно?

Делаю загрузку файлов на сервер. Хочу использовать потоки.

Я попытался кое-что сделать:

//FileSystem handler library

var log = require("core/lib/log")(module);

var fs = require('fs');

var async = require('async');



var fsh = function (files) {



    var $this = this;



    this.moveUploadedFiles = function(dest,cb){

        if(!Object.keys(files).length){

            log.info('fsh.moveUploadedFiles-> files object is empty');

            return cb({state:0}); //files not found

        }



        async.waterfall ([
            function (cb) {

                $this.createFolder(dest,function(){

                    cb(null);

                });

            }

        ], function () {

            var infile = [];

            var outfile = [];

            var uploadSize = [];

            for (var i in files) {

                var path = dest + '/' + files.originalFilename;

                infile = fs.createReadStream(files.path);

                outfile = fs.createWriteStream(path);

                infile.on('data',function(data) {

                    if(!uploadSize){

                        uploadSize = 0;

                    }

                    uploadSize += data.length/1024;

                    console.log(files.originalFilename + ': '+(files.size/1024) + '/'+uploadSize+' Kb');

                    outfile.write(data);

                });

                infile.on('close', function() {

                    outfile.close();

                });

                infile.pipe(outfile);

            }

        });



        return cb({state:1});  //upload success

    };



    this.createFolder = function(dir,cb){

        fs.exists(dir, function (exists) {

            if(exists){

                log.info('fsh.createFolder-> Dir exist: %s',dir);

                return cb();

            }else{

                fs.mkdir(dir,777,function(){

                    log.info('fsh.createFolder-> %s',dir);

                    return cb();

                });

            }

        });

    };





};



module.exports = fsh;

но как-то неправильно работает, несколько файлов за раз не пишет, работает только с одним. Я выбрал два разных файла, в консоли вижу следующее:

Hawaii-Big-Island-TF.jpg: 1323.076171875/64 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/128 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/192 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/256 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/320 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/384 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/448 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/512 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/576 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/640 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/704 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/768 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/832 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/896 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/960 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/1024 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/1088 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/1152 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/1216 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/1280 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/1344 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/1408 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/1472 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/1536 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/1600 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/1664 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/1728 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/1792 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/1856 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/1920 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/1984 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/2048 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/2112 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/2176 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/2240 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/2304 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/2368 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/2432 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/2496 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/2560 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/2624 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/2688 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/2752 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/2816 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/2880 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/2944 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/3008 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/3072 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/3136 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/3200 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/3264 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/3328 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/3392 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/3456 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/3520 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/3584 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/3597.8701171875 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/3661.8701171875 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/3725.8701171875 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/3789.8701171875 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/3853.8701171875 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/3917.8701171875 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/3981.8701171875 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/4045.8701171875 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/4109.8701171875 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/4173.8701171875 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/4237.8701171875 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/4301.8701171875 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/4365.8701171875 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/4429.8701171875 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/4493.8701171875 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/4557.8701171875 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/4621.8701171875 Kb

Hawaii-Big-Island-TF.jpg: 1323.076171875/4664.9462890625 Kb

В чем может быть проблема?